feat: filter out empty IDs when getting busy study group members and make the members select field live.

app/Filament/Pages/Learning/StudyGroup/Index.php

@@ -148,6 +148,7 @@ public function studyGroupFormSchema(): array
                         ->multiple()
                         ->searchable()
                         ->required()
+                        ->live()
                         ->columnSpanFull(),
 
                     TextInput::make('name')

app/Models/StudyGroup.php

@@ -65,6 +65,6 @@ function ($q) use ($courseIds, $excludeGroupId) {
             ->pluck('leader_id')
             ->toArray();
 
-        return array_unique(array_merge($busyMemberIds, $busyLeaderIds));
+        return array_unique(array_filter(array_merge($busyMemberIds, $busyLeaderIds)));
     }
 }